Psoriatic Arthritis (cont.)

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Catherine Burt Driver, MD

Catherine Burt Driver, MD, is board certified in internal medicine and rheumatology by the American Board of Internal Medicine. Dr. Driver is a member of the American College of Rheumatology. She currently is in active practice in the field of rheumatology in Mission Viejo, Calif., where she is a partner in Mission Internal Medical Group.

What causes psoriatic arthritis?

The cause of psoriatic arthritis is currently unknown. A combination of genetic, immune, and environmental factors is likely involved. In patients with psoriatic arthritis who have arthritis of the spine, a blood test gene marker called HLA-B27 is found in about 50%. Several other genes have also been found to be more common in patients with psoriatic arthritis. Certain changes in the immune system may also be important in the development of psoriatic arthritis. For example, the decline in the number of immune cells called helper T cells in people with AIDS (HIV infection) may play a role in the development and progression of psoriasis in these patients. The importance of infectious agents and other environmental factors in the cause of psoriatic arthritis is being investigated by researchers.

What are risk factors for developing psoriatic arthritis?

The major risk factor for developing psoriatic arthritis is having a family member with psoriasis. This relationship has been recognized as so significant that it is used as a helpful part of the history for the doctor to diagnose psoriatic arthritis. It might be that stressful life situations could affect the immune system, allowing for the expression and/or exacerbation of psoriatic arthritis. However, precisely how these emotional issues are related to psoriatic arthritis has not been established.

What are psoriatic arthritis symptoms and signs?

In most patients, the psoriasis precedes the arthritis by months to years. There can be tiny pitting nail changes of the finger and toenails. The type of psoriatic arthritis depends on the distribution of the joints affected. Accordingly, there are five types of psoriatic arthritis: symmetrical, asymmetric and few joints, spondylitis, distal interphalangeal joints, and arthritis mutilans.

The arthritis frequently involves the knees, ankles, and joints in the feet. Usually, only a few joints are inflamed at a time. The inflamed joints become painful, stiff, swollen, hot, tender, and red. There is usually loss of range of motion of the involved joints. Sometimes, joint inflammation in the fingers or toes can cause swelling of the entire digit, giving them the appearance of a "sausage." Joint stiffness is common and is typically worse early in the morning. Less commonly, psoriatic arthritis may involve many joints of the body in a symmetrical fashion, mimicking the pattern seen in rheumatoid arthritis. Psoriatic arthritis can also cause inflammation of the spine (spondylitis) and the sacrum, causing pain and stiffness in the low back, buttocks, neck, and upper back. Occasionally, psoriatic arthritis involves the small joints at the ends of the fingers. A very destructive, though less common, form of arthritis called "mutilans" can cause rapid damage to the joints. Fortunately, this form of arthritis is rare in patients with psoriatic arthritis.

Patients with psoriatic arthritis can also develop inflammation of the tendons (tendinitis) and around cartilage. Inflammation of the tendon behind the heel causes Achilles tendinitis, leading to pain with walking and climbing stairs. Inflammation of the chest wall and of the cartilage that links the ribs to the breastbone (sternum) can cause chest pain, as seen in costochondritis.

Aside from arthritis and spondylitis, psoriatic arthritis can cause fatigue and inflammation in other organs, such as the eyes, lungs, and aorta. Inflammation in the colored portion of the eye (iris) causes iritis, a painful condition that can be aggravated by bright light as the iris opens and closes the opening of the pupil. Corticosteroids injected directly into the eyes are sometimes necessary to decrease inflammation and prevent blindness. Inflammation in and around the lungs (pleuritis) causes chest pain, especially with deep breathing as the lungs expand against the inflamed areas, as well as shortness of breath. Inflammation of the aorta (aortitis) can cause leakage of the aortic valves, leading to heart failure and shortness of breath.

Acne and nail changes are commonly seen in psoriatic arthritis. Pitting and ridges are seen in fingernails and toenails of 80% of patients with psoriatic arthritis. Interestingly, these characteristic nail changes are observed in only a minority of psoriasis patients who do not have arthritis. Acne has been noted to occur in higher frequency in patients with psoriatic arthritis. In fact, a syndrome exists that features inflammation of the joint lining (synovitis), acne, pustules on the feet or palms, thickened and inflamed bone (hyperostosis), and bone inflammation (osteitis). This syndrome is, therefore, named by the eponym SAPHO syndrome.